title: Differential gene expression and adherence of Escherichia coli O157:H7 in vitro and in ligated pig intestines.
abstract: BACKGROUND
  Escherichia coli O157:H7 strain 86-24 grown in MacConkey broth (MB) shows almost no adherence to cultured epithelial cells but adheres well in pig ligated intestines. This study investigated the mechanisms associated with the difference between in-vitro and in-vivo adherence of the MB culture.
  
  
  RESULTS
  It was found that decreased adherence in vitro by bacteria grown in MB was mainly due to lactose, possibly implicating the involvement of carbon catabolite repression (CCR). Expression of selected virulence-related genes associated with adherence and CCR was then examined by quantitative PCR. When bacteria were grown in MB and Brain Heart Infusion with NaHCO(3) (BHIN) plus lactose, pH was reduced to 5.5-5.9 and there was a significant decrease in expression of the locus of enterocyte effacement (LEE) genes eae, tir, espD, grlA/R and ler, and an increase in cya (cAMP), and two negative regulators of the LEE, gadE and hfq. Putative virulence genes stcE, hlyA, ent and nleA were also decreased in vitro. Reversal of these changes was noted for bacteria recovered from the intestine, where transcripts for qseF and fis and putative virulence factors AidA(15), TerC and Ent/EspL2 were significantly increased, and transcripts for AIDA(48), Iha, UreC, Efa1A, Efa1B, ToxB, EhxA, StcE, NleA and NleB were expressed at high levels.
  
  
  CONCLUSIONS
  Presence of lactose resulted in decreased expression of LEE genes and the failure of EHEC O157:H7 to adhere to epithelial cells in vitro but this repression was overcome in vivo. CCR and/or acidic pH may have played a role in repression of the LEE genes. Bacterial pathogens need to integrate their nutritional metabolism with expression of virulence genes but little is known of how this is done in E. coli O157:H7. This study indicates one aspect of the subject that should be investigated further.
authors.affiliation: Guelph Food Research Center, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Xianhua
authors.initials: X
authors.lastname: Yin
authors.forename: Jing
authors.initials: J
authors.lastname: Zhu
authors.forename: Yanni
authors.initials: Y
authors.lastname: Feng
authors.forename: James R
authors.initials: JR
authors.lastname: Chambers
authors.forename: Joshua
authors.initials: J
authors.lastname: Gong
authors.forename: Carlton L
authors.initials: CL
authors.lastname: Gyles
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D001647:Bile Acids and Salts / Q000494:pharmacology; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects / Q000382:microbiology / Q000473:pathology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D005260:Female; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D007422:Intestines / Q000382:microbiology* / Q000473:pathology / Q000601:surgery; D007785:Lactose / Q000494:pharmacology; D008026:Ligation; D013552:Swine / Q000382:microbiology*
chemical_list: D001647:Bile Acids and Salts; D007785:Lactose